Why do truck drivers bash drivers for Schneider and Swift, and related companies?

I'm not a trucker myself, but I've always wondered, why do other truck drivers always bash people who drive for Schneider or Swift? I don't know if I should have an opinion because I don't drive a truck myself but the way I see it, driving a truck is driving a truck, and it's such a needed service so we should be more appreciative of the drivers regardless of who they work for because I know that no matter what it is not an easy job. I know that a lot of truckers go through a lot of trouble on the road sometimes, so I'm just curious, what's with all the criticism of who you work for?